CDMA Technology OverviewFebruary, 2001 - Page 3-1CDMA Technology OverviewLesson 4 - CDMA Reverse ChannelsCDMA Technology OverviewFebruary, 2001 - Page 3-2Access ChannelsCDMA Technology OverviewFebruary, 2001 - Page 3-3REG1-8002424444BTSCode Channels in the Reverse DirectionThere are two types of CDMA Reverse Channels:nTRAFFIC CHANNELS are used by individualusers during their actual calls to transmit trafficto the BTSa reverse traffic channel is defined by a user-specific public or private Long Code maskthere are as many reverse Traffic Channels asthere are CDMA phones in the worldnACCESS CHANNELS are used by mobile stations not yet in a call to transmit registration requests, call setup requests, page responses, order responses, and other signaling informationan access channel is defined by a user-independent public long code maskAccess channels are paired with Paging Channels. There can be up to 32 access channels per paging channelCDMA Technology OverviewFebruary, 2001 - Page 3-4MTXBSCBTS (1 sector)Channel ElementAccess ChannelsVocoderVocoderVocoderVocodermoremoreReceiver,Sector XChannel ElementChannel ElementChannel ElementChannel ElementLong Code GenLong Code GenLong Code GenLong Code GenLong Code GenmoreUserLongCodeUserLongCodeUserLongCodeUserLongCodeUserLongCodeUserLongCodeCoding Process in the Reverse DirectionA Reverse Channel is identified by:vits CDMA RF carrier Frequencyvthe unique Long Code PN Offset of the individual handsetCDMAFrequencyCDMA Technology OverviewFebruary, 2001 - Page 3-5Access ChannelsnUsed by the mobile station toInitiate communication with the base stationRespond to Paging Channel messagesnHas a fixed data rate of 4800 bpsnEach Access Channel is associated with only one Paging ChannelnUp to 32 access channels (0-31) are supported per Paging Channel4800 bpsCDMA Technology OverviewFebruary, 2001 - Page 3-6Access Channel GenerationnMessage attempts are randomized to reduce probability of collisionnTwo message types:A response message (in response to a base station message)A request message (sent autonomously by the mobile station)28.8kspsConvolutionalEncoder &RepetitionR = 1/31.2288McpsAccess ChannelLong Code MaskLong PN CodeGenerator28.8kspsOrthogonalModulation307.2kcps1.2288McpsQ PN (No Offset)I PN (No Offset)D1/2 PNChipDelayBlockInterleaverAccess ChannelInformation(88 bits/Frame)4.8 kpbsDirectSequenceSpreadingCDMA Technology OverviewFebruary, 2001 - Page 3-7Rate 1/3 Convolutional Encoder+g0g1g2Information bits(INPUT)Code Symbols(OUTPUT)Code Symbols(OUTPUT)Code Symbols(OUTPUT)12345678CDMA Technology OverviewFebruary, 2001 - Page 3-8Access Channel Block Interleavingn576 code symbols (288 x 2) are written sequentially by columns, then read by rows in a particular order (called “bit-reverse readout of the row addresses”) every 20 msnBlock interleaving separates repeated symbols in two identical sets: one set is transmitted during the first 10 ms and the second set, with the repetitions, is transmitted during the second 10 msImproves survivability of symbol information“Spreads” the effect of spurious interference and fast fading28.8 ksps fromConv. Encoding& SymbolRepetition (2x)Input Array(Normal Sequence)32 x 18Output Array(ReorderedSequence)32 x 1828.8 ksps toOrthogonalModulationCDMA Technology OverviewFebruary, 2001 - Page 3-9Access Channel Block Interleaving(4800 x 2 bps - Write Matrix) 1 17 33 49 65 81 97 113 129 145 161 177 193 209 225 241 257 273 1 17 33 49 65 81 97 113 129 145 161 177 193 209 225 241 257 273 2 18 34 50 66 82 98 114 130 146 162 178 194 210 226 242 258 274 2 18 34 50 66 82 98 114 130 146 162 178 194 210 226 242 258 274 3 19 35 51 67 83 99 115 131 147 163 179 195 211 227 243 259 275 3 19 35 51 67 83 99 115 131 147 163 179 195 211 227 243 259 275 4 20 36 52 68 84 100 116 132 148 164 180 196 212 228 244 260 276 4 20 36 52 68 84 100 116 132 148 164 180 196 212 228 244 260 276 5 21 37 53 69 85 101 117 133 149 165 181 197 213 229 245 261 277 5 21 37 53 69 85 101 117 133 149 165 181 197 213 229 245 261 277 6 22 38 54 70 86 102 118 134 150 166 182 198 214 230 246 262 278 6 22 38 54 70 86 102 118 134 150 166 182 198 214 230 246 262 278 7 23 39 55 71 87 103 119 135 151 167 183 199 215 231 247 263 279 7 23 39 55 71 87 103 119 135 151 167 183 199 215 231 247 263 279 8 24 40 56 72 88 104 120 136 152 168 184 200 216 232 248 264 280 8 24 40 56 72 88 104 120 136 152 168 184 200 216 232 248 264 280 9 25 41 57 73 89 105 121 137 153 169 185 201 217 233 249 265 281 9 25 41 57 73 89 105 121 137 153 169 185 201 217 233 249 265 28110 26 42 58 74 90 106 122 138 154 170 186 202 218 234 250 266 28210 26 42 58 74 90 106 122 138 154 170 186 202 218 234 250 266 28211 27 43 59 75 91 107 123 139 155 171 187 203 219 235 251 267 28311 27 43 59 75 91 107 123 139 155 171 187 203 219 235 251 267 28312 28 44 60 76 92 108 124 140 156 172 188 204 220 236 252 268 28412 28 44 60 76 92 108 124 140 156 172 188 204 220 236 252 268 28413 29 45 61 77 93 109 125 141 157 173 189 205 221 237 253 269 28513 29 45 61 77 93 109 125 141 157 173 189 205 221 237 253 269 28514 30 46 62 78 94 110 126 142 158 174 190 206 222 238 254 270 28614 30 46 62 78 94 110 126 142 158 174 190 206 222 238 254 270 28615 31 47 63 79 95 111 127 143 159 175 191 207 223 239 255 271 28715 31 47 63 79 95 111 127 143 159 175 191 207 223 239 255 271 28716 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 28816 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288CDMA Technology OverviewFebruary, 2001 - Page 3-10Access Channel Block Interleaving(4800 x 2 bps - Read Matrix) 1 17 33 49 65 81 97 113 129 145 161 177 193 209 225 241 257 273 9 25 41 57 73 89 105 121 137 153 169 185 201 217 233 249 265 281 5 21 37 53 69 85 101 117 133 149 165 181 197 213 229 245 261 27713 29 45 61 77 93 109 125 141 157 173 189 205 221 237 253 269 285 3 19 35 51 67 83 99 115 131 147 163 179 195 211 227 243 259 27511 27 43 59 75 91 107 123 139 155 171 187 203 219 235 251 267 283 7 23 39 55 71 87 103 119 135 151 167 183 199 215 231 247 263 27915 31 47 63 79 95 111 127 143 159 175 191 207 223 239 255 271 287 2 18 34 50 66 82 98 114 130 146 162 178 194 210 226 242 258 27410 26 42 58 74 90 106 122 138 154 170 186 202 218 234 250 266 282 6 22 38 54 70 86 102 118 134 150 166 182 198 214 230 246 262 27814 30 46 62 78 94 110 126 142 158 174 190 206 222 238 254 270 286 4 20 36 52 68 84 100 116 132 148 164 180 196 212 228 244 260 27612 28 44 60 76 92 108 124 140 156 172 188 204 220 236 252 268 284 8 24 40 56 72 88 104 120 136 152 168 184 200 216 232 248 264 28016 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288 1 17 33 49 65 81 97 113 129 145 161 177 193 209 225 241 257 273 9 25 41 57 73 89 105 121 137 153 169 185 201 217 233 249 265 281 5 21 37 53 69 85 101 117 133 149 165 181 197 213 229 245 261 27713 29 45 61 77 93 109 125 141 157 173 189 205 221 237 253 269 285 3 19 35 51 67 83 99 115 131 147 163 179 195 211 227 243 259 27511 27 43 59 75 91 107 123 139 155 171 187 203 219 235 251 267 283 7 23 39 55 71 87 103 119 135 151 167 183 199 215 231 247 263 27915 31 47 63 79 95 111 127 143 159 175 191 207 223 239 255 271 287 2 18 34 50 66 82 98 114 130 146 162 178 194 210 226 242 258 27410 26 42 58 74 90 106 122 138 154 170 186 202 218 234 250 266 282 6 22 38 54 70 86 102 118 134 150 166 182 198 214 230 246 262 27814 30 46 62 78 94 110 126 142 158 174 190 206 222 238 254 270 286 4 20 36 52 68 84 100 116 132 148 164 180 196 212 228 244 260 27612 28 44 60 76 92 108 124 140 156 172 188 204 220 236 252 268 284 8 24 40 56 72 88 104 120 136 152 168 184 200 216 232 248 264 28016 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288CDMA Technology OverviewFebruary, 2001 - Page 3-11Access Channel StructureAccess Channel Message Padding CRC 20 ms96 bits8 x MSG_LENGTH8 bits30 bitsMSG_LENGTH2-842 bitsasrequiredAccess Channel Frame Message Body 20 x (4 + PAM_SZ + MAX_CAP_SZ) ms96 x (4 + PAM_SZ + MAX_CAP_SZ) bits4800 bpsNf =Number of AccessChannel Frames needed for message transmissionT = Encoder Tail Bits(eight zeroes)Access Channel Frame Body 1 + PAM_SZ frames96 x (1 + PAM_SZ) bits96 x Nf bits (not exceeding 3 + MAX_CAP_SZ frames)Access Channel SlotTAccess Channel PreambleAccess Channel Message CapsuleTTT88 x Nf bitsCDMA Technology OverviewFebruary, 2001 - Page 3-12Access Channel ProbingAccessProbe 1AccessProbe 1AccessProbe 1AccessProbe 1Access Probe1 + NUM_STEP(16 max)SystemTimeTARTTARTTARTTAPIPIPIIP(InitialPower)See previousfigureACCESSPROBESEQUENCESelect Access Channel (RA)initialize transmit powerCDMA Technology OverviewFebruary, 2001 - Page 3-13Reverse Traffic ChannelsCDMA Technology OverviewFebruary, 2001 - Page 3-14CDMA Reverse Traffic ChannelsnUsed when a call is in progress to sendVoice traffic from the subscriberResponse to commands/queries from the base station Requests to the base stationnSupports variable data rate operation for8 Kbps vocoder-Rate Set 1 - 9600, 4800, 2400 and 1200 bps-Multiplex Option 113 Kbps vocoder-Rate Set 2 - 14400, 7200, 3600, 1800 bps-Multiplex Option 2CDMA Technology OverviewFebruary, 2001 - Page 3-15Reverse Traffic Channel Generation9600 bps4800 bps2400 bps1200 bpsor 14400 bps7200 bps3600 bps1800 bps28.8kspsR = 1/31.2288McpsUser AddressMaskLongPN CodeGenerator28.8kspsOrthogonalModulationData BurstRandomizer307.2kcps1.2288McpsQ PN(no offset)I PN(no offset)D1/2 PNChipDelayDirectSequenceSpreadingR = 1/2ConvolutionalEncoder &RepetitionBlockInterleaverCDMA Technology OverviewFebruary, 2001 - Page 3-16Reverse Traffic Channel Frame StructureTransmissionRateTotalErasureInformationCRCTail Bits9600192172128480096808824004840812002416814400288126712872001441125108360072155881800361216812Number of Bits per FrameRateSetCDMA Technology OverviewFebruary, 2001 - Page 3-17Reverse Traffic Channel Convolutional Encoding & Symbol RepetitionnConvolutional encoding:Results in 3 code symbols out for each bit in, at Rate Set 1, and in 2 code symbols out for each bit in, at Rate Set 2Also allows for reduction in transmit powerReduces overall noise & increases capacitynSymbol repetition maintains a constant 28.8 ksps output to block interleaverPCM VoiceConvolutionalEncodingCode SymbolRepetitionBlockInterleavingOrthogonalModulationData BurstRandomizerDirect SequenceSpreadingQuadratureSpreadingBasebandFilteringVocoderProcessingBaseband Traffic to RF SectionVariableRateOutputfromVocoderR=1/3 K=9 ConvolutionalEncoderR=1/2 K=928.8 kspsto BlockInterleaver28.8 ksps (No repetition)14.4 ksps (2 X repetition)7.2 ksps (4 X repetition)3.6 ksps (8 X repetition)28.8 ksps (No repetition)14.4 ksps (2 X repetition)7.2 ksps (4 X repetition)3.6 ksps (8 X repetition)SymbolRepetition9.6 kbps4.8 kbps2.4 kbps1.2 kbps14.4 kbps 7.2 kbps 3.6 kbps 1.8 kbpsCDMA Technology OverviewFebruary, 2001 - Page 3-18Reverse Traffic Channel Block Interleavingn20 ms symbol blocks are sequentially reorderednCombats the effects of fast fadingnSeparates repeated symbols at 4800 bps and below Improves survivability of symbol data“Spreads” the effect of spurious interferencePCM VoiceConvolutionalEncodingCode SymbolRepetitionBlockInterleavingVocoderProcessingBaseband Traffic to RF SectionOrthogonalModulationData BurstRandomizerDirect SequenceSpreadingQuadratureSpreadingBasebandFiltering28.8 kspsFrom Coding& SymbolRepetitionOutput Array(ReorderedSequence)32 x 1828.8 ksps toOrthogonalModulationInput Array(Normal Sequence)32 x 18CDMA Technology OverviewFebruary, 2001 - Page 3-19Lesson Review1.The two types of CDMA Reverse Channels are Traffic Channels and Access Channels. True/FalseTrue2.Short PN sequences are used to achieve _.Phase Modulation3.How many access channels are supported by a single paging channel?32 (0 - 31)4.When generating the Access Channel, why are message attempts randomized?To reduce the probability of collision5.What is the access channel preamble?A frame comprised of 96 zeroes that aids the base station in acquiring access channel transmission.CDMA Technology OverviewFebruary, 2001 - Page 3-20Lesson Review, contd6.All Access Channels associated with a particular Paging Channela. have the same slot sizeb. do not have the same slot sizec. all slots begin at the same timed. all slots do not begin at the same timee. a and cf. a and dg. none of the abovea and c7.Why is the Reverse Traffic Channel preamble transmitted by the mobile to the base station?To help the base station acquire the Reverse Traffic Channel8.The pilot PN sequences are offset relative to system time, not mobile station time. Why?The mobile draws its time reference from the earliest usable pilot component it receives.9.What is used in the reverse path: direct sequence spreading or data scrambling?Direct sequence spreadingCDMA Technology OverviewFebruary, 2001 - Page 3-21